shaefins
Senior Member
Posts: 161
Joined: Wed Mar 24, 2010 11:17 pm
Location: Pittsburgh, 6A

Dirt help, please.

32 sq ft raised bed - box is 16" high. How deep do I need my soil mix to be?

And if there are any algebra whizzes out there that can give me a formula to figure out how much soil I need based on the size of the box and the depth of the soil, I would be forever grateful! :D

DoubleDogFarm
Super Green Thumb
Posts: 6113
Joined: Mon Mar 29, 2010 3:43 am

shaefins.


I'd go at least 12" deep up to 14". I'll do 12 for the math.

48" x 96" X 12" = 55296 cubic inches divided by 1728. = 32 cubic feet

That's the long way.

32sq ft x 1ft = 32cu ft. divided by 27 = 1.185 yards of soil

1.5 will fill the box

cynthia_h
Super Green Thumb
Posts: 7501
Joined: Tue May 06, 2008 11:02 pm
Location: El Cerrito, CA

Between us, DDF and I will get you to where you'll be able to figure out how much it will take to fill any box, any time, anywhere! (This assumes you're using the American measurement system, not the metric system.)

1) Formula: Length x Width x Depth ==> make sure all are in the same unit (inches)

2) Convert to Cubic Feet: The Magic Number = 1728 (because 12 x 12 x 12 = 1728, the number of cubic inches in 1 cubic foot). Divide #1 inches by 1728.

3) That's It! You now have the number of cubic feet of [soil, compost] needed to fill the raised bed/swimming pool/large hole in the ground. :wink:

Just for comparison, here's the metric calculation for a raised bed like yours, filled to the same depth.

260 cm x 130 cm x 30 cm =
2.6 m x 1.3 m x 0.3 m = 1.014 m^3

:D

Cynthia H.
Sunset Zone 17, USDA Zone 9

shaefins
Senior Member
Posts: 161
Joined: Wed Mar 24, 2010 11:17 pm
Location: Pittsburgh, 6A

While it's my dream to expatriate to Europe, the Metric System is *not* my thing! :lol:

Thank you both - that formula is a HUGE help!

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